Traffic engineering (TE) is a technology that is concerned with performance optimization of operational networks. In general, TE includes a set of applications mechanisms, tools, and scientific principles that allow for measuring, modeling, characterizing and control of user data traffic in order to achieve specific performance objectives.
Multiprotocol label switching (MPLS) is a scheme in a high-performance telecommunication network which directs and carries data from one node to the next node in the network. In MPLS, labels are assigned to data packets, and packet forwarding decisions from one node to the next node in the network are made based on the contents of the label for each data packet, without the need to examine the data packet itself.
Generalized Multiprotocol Label Switching (GMPLS) is a type of protocol which extends MPLS to encompass network schemes based upon time-division multiplexing (e.g. SONET/SDH, PDH, G.709), wavelength multiplexing, and spatial switching (e.g. incoming port or fiber to outgoing port or fiber). Multiplexing, such as time-division multiplexing is when two or more signals or bit streams are transferred over a common communication link. In particular, time-division multiplexing (TDM) is a type of digital multiplexing in which two or more signals or bit streams are transferred as sub-channels in one communication link, but are physically taking turns on the communication link. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. After the last sub-channel, the cycle starts over again. Time-division multiplexing is commonly used for circuit mode communication with a fixed number of communication links and constant bandwidth per link. Time-division multiplexing differs from statistical multiplexing, such as packet switching, in that the timeslots are returned in a fixed order and preallocated to the channels, rather than scheduled on a packet by packet basis.
An Optical Transport Network (OTN) is comprised of a plurality of switch nodes linked together to form the OTN. The OTN includes an electronic layer and an optical layer. The electronic layer and the optical layer each contain multiple sub-layers. The optical layer provides optical connections between the nodes, also referred to as optical channels or lightpaths, to other layers, such as the electronic layer. The optical layer performs multiple functions, such as monitoring network performance, multiplexing wavelengths, and switching and routing wavelengths. In general, OTNs are a combination of the benefits of SONET/SDH technology and wave division multiplexing (WDM) or dense wavelength-division multiplexing (DWDM) technology (optics). OTN structure, architecture, and modeling are further described in the International Telecommunication Union recommendations, including ITU-T G.709, ITU-T G.872, and ITU-T G.805, which are well known in the art.
The optical transport hierarchy (OTH) of OTNs supports the operation and management aspects of OTNs of various architectures, e.g., point-to-point, ring, and mesh architectures. One part of the optical transport hierarchy is a multiplex hierarchy, which is a hierarchy including an ordered repetition of tandem digital multiplexers that produce signals of successively higher data rates at each level of the hierarchy. Multiplexing hierarchy may be specified by way of optical channel data units, i.e., ODUj, where j varies from 0 to 4; and optical channel transport units, i.e., OTUk, where k varies from 1 to 4. The optical channel data units refer to a frame format for transmitting data which can be either fixed in the data rate or the data rate can be arbitrarily set.
Examples of optical channel data units that are fixed in the amount of data and data rate include those specified by ODU0, ODU1, ODU1e, ODU2, ODU2e, ODU3, ODU3e1, ODU3e2, and ODU4. An example of an optical channel data unit in which the data rate can be arbitrarily set is referred to in the art as ODUflex, which allows adjustments to the size of the ODUflex by adding or removing timeslots.
The optical channel data units within the multiplexing hierarchy are referred to in the art as lower order or higher order. A higher order optical channel data unit refers to a server layer to which a lower order optical channel data unit (client layer) is mapped to. Optical channel data units include a parameter referred to as tributary slot granularity which refers to a data rate of the timeslots within the optical channel data unit. The tributary slot granularity of optical channel data units include time slots of approximately 1.25 Gbit/s or 2.5 Gbit/s. OPUk (when k=1, 2, 3, 4) is divided into equal sized Tributary Slots or Time Slots of granularity (1.25G or 2.5G) to allow mapping of lower order ODUj (where j<k). For example: On OPU4, there are 80 (1.25G) Tributary Slots. To map: ODU3 into OPU4=>31 TSs are used; ODU2/2e into OPU4=>8 TS are used; ODU1 into OPU4=>2 TSs are used; and ODU0 into OPU4=>1 TS is used.
Multi-stage ODU multiplexing, refers to an OTN multiplexing hierarchy in which an ODUi container can first be multiplexed into a higher order ODUj container, which is then multiplexed into a higher order-ODUk container. A single-stage multiplexing refers to one lower order ODUj multiplexed into a higher order ODUk. The single stage ODU multiplexing can be heterogeneous (meaning lower order ODUj of different rates can be multiplexed into a higher order ODUk).
OTNs support switching at two layers: (i) ODU Layer, i.e., time division multiplexing and (ii) OCH Layer—Lambda or wavelength switching where OCH stands for Optical Channel. The nodes in the OTN may support one or both the switching types. When multiple switching types are supported Multi-Layer Network (MLN) based routing as described in [RFC5339] is assumed.
Bandwidth is the data transfer capacity of a link, path, or connection, which may be expressed in optical data units, bits per second, number of time slots, or expressed by other methods. The bandwidth for fixed ODU rates can be advertised as a number of containers. The bandwidth for variable ODU rates such as ODUflex can be advertised as a data rate, such as bytes/second and/or as a number of timeslots. The TE-link bandwidth information can be saved in a link state database and used for computing routes or paths in the OTN for setting up optical channel data unit label switched paths in networks having multiple nodes communicating via communication links.
Currently, IP traffic (e.g., including user packet flows) is transported over P-OTN networks using OTN or WDM/DWDM pipes (e.g., label switched paths), such as via one or more ODU containers which are transported through the OTN via a label switched path (e.g., using GMPLS) typically setup by a headend node. The OTN typically statically provisions WDM/DWDM pipes by reserving a certain amount of bandwidth, e.g., by statically provisioning label switch paths in the OTN based on a connection setup signal transmitted by a headend node which measures maximum traffic over an incoming IP link. Additional bandwidth may be reserved or allocated if measured maximum IP-traffic increases above the measured maximum traffic.
However, existing static methodologies for bandwidth provisioning are lacking in several aspects. Because IP links do not carry the maximum measured traffic all the time, static bandwidth provisioning models currently result in OTN transport pipes or paths being underutilized for a large portion of the time, by not fully utilizing the reserved time slots for a particular transport path when IP-traffic with a rate lower than the maximum measured rate is carried by the transport paths. This uses up timeslots and bandwidth in the OTN that may be used by users for other services, or may be sold to other users by the network operator.